This invention relates to a body fluid testing device and methods for obtaining samples of blood fluid for analysis.
Many medical procedures in use today require a relatively small sample of body fluid, for example in the range of 0.1-50 micro liters. It is more cost effective and less traumatic to the patient to obtain such a sample by lancing or piercing the skin at a selected location, such as the finger or forearm, to enable the collection body fluid. With the advent of home use tests for the self monitoring of blood glucose, there is a requirement for a simple procedure which can be performed in any setting without a person needing the assistance of a professional.
One device which is commonly utilized to form an opening in the patient""s skin is a lancets. Lancets generally have a rigid body and a sterile lance which protrudes from one end. The lancet may be used to pierce the skin, thereby enabling the collection of a body fluid sample from the opening created. The body fluid sample is transferred to a test device or collection device. Body fluid is most commonly taken from the fingertips, where the supply is generally excellent. However, the nerve density in this region causes significant pain in many patient""s. Sampling of alternative sites, such as earlobes and limbs is sometimes practiced to lessen the pain. These sites are also less likely to provide excellent body fluid samples and make body fluid transfer directly to test devices difficult. Examples of body fluids which may be utilized to test for glucose are blood and interstitial fluid.
Repeated lancing in limited surface areas, such as fingertips, results in callous formation. This leads to increased difficulty in drawing body fluid and increased pain.
To reduce the anxiety of piercing the skin and the associated pain, many spring loaded devices have been developed wherein the device automatically triggers in response to an applied force. Thus the user cannot anticipate the exact timing of the piercing, thus they are less likely to pull the device away during use. The following two patents are representative of the devices which were developed in the 1980""s for use with home diagnostic test products.
U.S. Pat. No. 4,503,856, Cornell et al., describes a spring loaded lancet injector. The reusable device interfaces with a disposable lancet. The lancet holder may be latched in a retracted position. When the user contacts a release, a spring causes the lancet to pierce the skin at high speed and the retract. The speed is important to reduce the pain associated with the puncture.
Levin et al., U.S. Pat. No. 4,517,978 describes a blood sampling instrument. This device, which is also spring loaded, uses a standard disposable lancet. The design enables easy and accurate positioning against a fingertip so the impact site can be readily determined. After the lancet pierces the skin, a bounce back spring retracts the lancet to a safe position within the device.
In home settings it is often desirable to collect a body fluid sample in order to enable a user to perform a test at home, such as glucose monitoring. Some blood glucose monitoring systems, require that the blood sample be applied to a test device wich is in contact with the test instrument. In such situations, bringing the finger to the test device poses some risk of contamination of the sample with a previous sample that may not have been properly cleaned from the device. Glucose monitoring devices may utilize a blood sample in many ways, though the two most common methods for collection are a paper strip and a capillary tube. Monitors that utilize a paper strip, require the patient to pierce a finger or appropriate location, withdraw a small sample of blood from the pierced area, such as by squeezing, and then placing the paper strip in physical contact with the blood sample and waiting until the paper strip absorbs the blood. Monitors that utilize a capillary tube for fluid collection, require the patient to follow the process described above, except that a paper strip is not utilized, instead a small capillary tube is placed over the sample until a sufficient amount of blood is withdrawn into the capillary tube and to the glucose testing area of the testing device.
Many times due to dexterity problems or poor eye site it can be difficult for the patient to either bring the body fluid sample to the testing area or to bring a capillary tube to the fluid sample. Additionally, some patient""s have a fear of bodily fluids, such as blood, and would prefer not to see this type of body fluid.
Amira Medical Inc. introduced a new method for home glucose testing. Amira""s device AtLast 7, tests blood glucose levels by taking blood from the skin of the forearm, which is a much less sensitive than the fingertips. This device has been very well received by both the diabetic community as well as the blood glucose measurement industry.
Haynes, U.S. Pat. No. 4,920,977 describes a blood collection assembly with a lancet and micro-collection tube. This device incorporates a lancet and collection container in a single device. The lancing and collection are two separate activities, but the device is a convenient single disposable unit for situations when sample collection prior to use is desirable. Similar devices are disclosed in Sarrine. U.S. Pat. No. 4,360,016 and O""Brian, U.S. Pat. No. 4,924,879.
Jordan et al., U.S. Pat. No. 4,850,973 and U.S. Pat. No. 4,858,607 disclose a combination device which may be alternatively used as a syringe-type injection device and a lancing device with disposable solid needle lancet, depending on configuration.
Lange et al., U.S. Pat. No. 5,318,584 describes a blood lancet device for withdrawing blood for diagnostic purposes. This invention uses a rotary/sliding transmission system to reduce the pain of lancing. The puncture depth is easily and precisely adjustable by the user.
Suzuki et al., U.S. Pat. No. 5,368,047, Dombrowski, U.S. Pat. No. 4,654,513 and Ishibashi, et al., U.S. Pat. No. 5,320,607 each describe suction-type blood samplers. These devices develop suction between the lancing site and the end of the device with the lancet holding mechanism withdraws after piercing the skin. A flexible gasket around the end of the device helps seal the end around the puncture site until adequate sample is withdrawn from the puncture sire or the user pulls the device back.
Garcia et al., U.S. Pat. No. 4,637,403 discloses a combination lancing and blood collection device which uses a capillary action passage to conduct body fluid to a separate test strip in the form of a micro porous membrane. It is necessary to achieve a precise positioning of the upper end of the capillary passage with respect o the membrane in order to ensure that the body fluid from the passage is transferred to the membrane. If an appreciable gap exits therebetween, no transfer may occur.
It is difficult for a user to determine whether a sufficiently large drop of body fluid has been developed at the incision for providing a large enough sample.
Single use devices have also been developed for single use tests, i.e. home cholesterol testing, and for institutional use to eliminate the cross-patient contamination multi-patient use. Crosman et al., U.S. Pat. No. 4,869,249, and Swierczek, U.S. Pat. No. 5,402,798, also describe disposable, single use lancing devices.
The disclosures of the above patents are incorporated herein by reference.
An object of the present invention is to provide a one-step procedure and device for testing glucose levels in body fluids.
Another object of the present invention is to provide an apparatus that withdraws a body fluid sample and provides an individual with a body fluid glucose level reading.
Even with the many improvements which have been made, the pain associated with lancing remains a significant issue for many patients. The need for blood sampling and the fear of the associated pain is also a major obstacle for the millions of diagnosed diabetics, who do not adequately monitor their blood glucose due to the pain involved. Moreover, lancing to obtain a blood sample for other diagnostic applications is becoming more commonplace, and a less painful, minimally invasive device is needed to enhance those applications and make those technologies more acceptable.
An object of the present invention therefore, is to provide a device and a method for obtaining a sample of bodily fluid through the skin which is virtually pain free and minimally invasive, particularly by penetrating less sensitive areas of the skin.
Furthermore, known lancing devices include manually actuable buttons for triggering the lance-driving mechanism once the user has placed the device against his/her skin. Because the user knows the precise instant when the lancet will be triggered and pain will be felt, there is a tendency for the user to jerk or raise the device at the instant of triggering, which can lead to inconsistent skin penetration, or possibly no penetration. Therefore, a further object of the invention is to provide a lancing device which eliminates such a tendency on the part of the user.
Therefore, it is another object of the invention to provide a lancet carrier which eliminates the above-mentioned shortcomings.
Another object of this invention is to provide a method which can result in a sample of either blood or interstitial fluid, depending on the sample site and the penetration depth utilized. While there are no commercially available devices utilizing interstitial fluid (ISF) at this time, there are active efforts to establish the correlation of analytes, such as glucose, in ISF compared to whole blood. If ISF could be readily obtained and correlation is established, ISF may be preferable as a sample since there is no interference of red blood cells or hematocrit adjustment required.
Another object of this invention is to provide a method by which the drawn sample is collected and may be easily presented to a testing device, regardless of the location of the sample site on the body. This approach helps with infection control in that multiple patients are not brought in contact with a single test instrument; only the sampling device with a disposable patient-contact portion is brought to the test instrument. Alternatively, the disposable portion of a test device may be physically coupled with the sampler so the sample can be brought directly into the test device during sampling. The test device may then be read in a test instrument if appropriate or the testing system can be integrated into the sampler and the test device can provide direct results displayed for the patient.
It is a further object of the invention is to provide a device for minimally invasive sampling comprising a reusable sampler and disposable sample lancet and collection device.
The present invention involves a method of obtaining a sample of fluid from a body. The method comprises applying a skin-lancing medium against a skin surface to form an incision therein, removing the skin-lancing medium from the incision; and thereafter applying a force to depress the skin in a manner forming a ring of depressed body tissue in surrounding relationship to the incision, causing the incision to bulge and the sides of the incision to open, whereby body fluid is forced out through the opening of the incision.
The invention also relates to a device for sampling body fluid which comprises a housing having an open end, and a skin lancing mechanism for applying a skin-lancing medium against a skin surface to form an incision therein and then remove the skin-lancing medium from the incision. A stimulator member is mounted to the housing at the open end thereof for movement relative to the housing. The stimulator member extends about a longitudinal axis of the housing and is adapted to engage the skin surface to bulge and open the incision in response to a pressing of the end face against the skin surface.
The invention also relates to a device for expressing body fluid from a lanced skin surface, which comprises a housing, and a stimulator mechanism mounted to the housing at an end thereof. The stimulator mechanism includes a generally circular array of stimulator elements each mounted to the housing for movement toward and away from a longitudinal axis of the housing. An actuator is mounted to the housing for displacing the stimulator elements toward the axis.
The invention also relates to a device for expressing body fluid from a lanced skin surface, which comprises a housing and a stimulator member mounted on the housing at an end thereof. The stimulator member comprises a coil spring which is compressible toward the housing in response to being pushed against a user""s skin in surrounding relationship to a lanced portion thereof.
Another aspect of the invention relates to a device for expressing body fluid from a lanced skin surface which comprises a housing and a hollow stimulator member mounted at an end of the housing and adapted to engage a user""s skin surface in surrounding relationship to a lanced portion thereof. In order to promote the flow of body fluid, the stimulator member can be heated, or vibrated. If vibrated, the stimulator member applies an ultrasonic frequency to the skin surface.
The invention also relates to a device for expressing body fluid from a lanced skin surface which comprises a housing and a hollow stimulator member mounted at an end of the housing for longitudinal movement relative to the housing and adapted to contact a user""s skin surface in surrounding relationship to a lanced portion thereof. A motor is mounted in the housing and a reciprocatory mechanism is connected to the motor to be driven thereby, and is operably connected to the stimulator member for reciprocating the stimulator member along a longitudinal axis of the stimulator member.